Watermarking of Motion Picture prints

ABSTRACT

An apparatus for marking a film copy includes a mapper and a coder. The maper maps a print identifier to be associated with the film copy into a serial number comprising a sequence of J numbers. The coder creates at least two-error correcting numbers, e.g. Y and Z, as a function of one, or more, of the J numbers. The film copy is then marked in accordance with L numbers, which comprise at least the two-error correcting numbers Y and Z.

BACKGROUND OF THE INVENTION

The inventive arrangements relate generally to the field of protectingmotion picture film against illegal copying, and in particular, to animproved method for film encoding to facilitate the identification ofthe source of copies encoded in accordance with the inventivearrangements.

Piracy issues in connection with the theatrical exhibition of motionpicture films are well known. Once a film distributor distributes printsof a motion picture film to exhibitors for theatrical exhibition, acertain degree of control over the product is lost. In the regularcourse of exhibiting the film, a customer in the theater maysurreptitiously record the film using, e.g., a hand held camcorder. At amore sophisticated level, a person seeking to obtain an illegal copy ofa film print may gain access to a theater projection booth in collusionwith an employee of the exhibitor and make a copy of the film afterhours in a relatively controlled environment. In such an environment,the audio from the projection equipment can be directly fed to thecamcorder. A tripod can be used to ensure a clear and steady picture. Asa result, an illicit copy can be made. Alternatively, the print itselfmay be scanned to create a video master.

In 1982, the Motion Picture Association of America (MPAA), together withthe Kodak Corporation, developed a technology for uniquely identifyingfilm prints. This technology is commonly known as Coded Anti-piracy(CAP) coding. The code is a series of faint dots in the picture that areadded as the print is manufactured. Approximately one out of everyhundred frames contains four tiny dots that have been added to theimage. Generally, 11 CAP-coded frames are required to reconstitute theserial number of the movie print. Each unique configuration of dotscorresponds to a print identifier. The film prints are usually coded foreach theater in which a film is distributed.

Historically, aiming an analog camcorder at a theater screen produced apoor quality, flickering image, but the coding dots usually survived thecopying and reproduction process so that the serial number of the movieprint could be obtained. The advent of digital video compression anddistribution technologies, however, has diminished the viability of CAPcoding. Improved digital camcorders not only take higher qualitypictures, but video compression algorithms, which are commonly employedwhen the pirated film is stored in a digital format or transported overthe internet, tend to obliterate the CAP codes. Specifically, becausethe dots representing the code are extremely small and diffuse, they aresusceptible to disintegration during video compression. Furthermore, theloss of a single CAP code dot during image compression can defeat theCAP coding scheme because the CAP code is represented by spatial imageplacement within the film frame. Therefore CAP coding is dependent upon100% image survival.

Another limitation of the CAP coding system is that a total of 2023unique configurations were developed in 1982. At the time, this wassufficient because it was roughly equivalent to the number of theatersin operation at the time and substantially exceeded the number of printsthat had been made in connection with even the largest motion picturereleases. Today there are over 20,000 theaters worldwide, and majormotion picture releases of more than 5,000 prints are increasinglycommon. Accordingly, there are an insufficient number of codes touniquely identify each film print that is distributed.

Further, the frequency of code image repetition in CAP coding systemsincreases the likelihood that the public will see the image. This isundesirable as it can distract viewers from the film content or causethem to form an opinion that a particular theater shows poor qualityprints. Accordingly, there is a pressing need for a successor to CAPcoding that allows the origin of the piracy to be identified.

SUMMARY OF THE INVENTION

In accordance with the principles of the invention, a sequence of Jnumbers represents a serial number for a film copy, from which at leasttwo error-correcting numbers, e.g., Y and Z, are created, where each isa function of one or more of the J numbers. The film copy is then markedin accordance with at least the two error-correcting numbers Y and Z.

In an embodiment of the invention, an apparatus for marking a film copyincludes a mapper and a coder. The mapper maps a print identifier to beassociated with the film copy into a serial number comprising a sequenceof J numbers. The coder creates at least two-error correcting numbers,e.g., Y and Z, as a function of one, or more, of the J numbers. The filmcopy is then marked in accordance with L numbers, which comprise atleast the two error-correcting numbers Y and Z.

In another embodiment of the invention, a method for marking a filmincludes the steps of mapping and coding. The mapping step maps a printidentifier to be associated with the film copy into a serial numbercomprising a sequence of J numbers. The coding step creates at leasttwo-error correcting numbers, e.g., Y and Z, as a function of one, ormore, of the J numbers. The film copy is then marked in accordance withL numbers, which comprise at least the two error-correcting numbers Yand Z.

In another embodiment of the invention, a motion picture is disposed ona medium, wherein the motion picture comprises a plurality of frames,each frame representing a portion of the motion picture; and whereinsome of the frames are marked to represent an erasure-correcting codedserial number; wherein the erasure-correcting coded serial numbercomprises L numbers, wherein N of the L numbers represent a portion of aserial number comprising J numbers, where N<J, the serial number beingassociated with the copy of the motion picture, and the remainder of theL numbers represent error-correcting numbers derived as a function ofone, or more, of the J numbers.

In another embodiment of the invention, a motion picture is disposed ona medium, wherein the motion picture comprises a plurality of frames,each frame representing a portion of the motion picture; and whereinsome of the frames are marked to represent an erasure-correcting codedserial number; wherein the erasure-correcting coded serial numbercomprises L numbers, and wherein the erasure-correcting coded serialnumber enables recovery of a print identifier associated with the copyof the motion picture if M of the L numbers are subsequently missing,where M>1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a motion picture stored on amedia that is useful for understanding the invention.

FIGS. 2A and 2B are diagrams that are useful for showing how differentmarkings can be used to mark different prints of a film.

FIG. 3 shows a frame containing an image that has been marked.

FIG. 4 is a block diagram that is useful for understanding an apparatusof the invention for marking a motion picture.

FIG. 5 is an exemplary sequence for serial number recovery from a motionpicture print copy serialized in accordance with various inventivearrangements.

FIG. 6 shows an illustrative encoder for marking film in accordance withthe principles of the invention.

FIG. 7 shows an illustrative flow chart in accordance with theprinciples of the invention.

FIGS. 8 and 9 show illustrative tables for use in recovering a printidentifier in accordance with the principles of the invention.

FIGS. 10 and 11 show illustrative encoders for marking film inaccordance with the principles of the invention.

DETAILED DESCRIPTION

Motion pictures are commonly distributed to theaters around the worldfor exhibition. Accordingly, in order to distribute the motion pictureto many locations simultaneously, multiple production copies of themotion picture are typically produced on a suitable media. Film ispresently the most common media on which motion pictures are distributedto theaters. For example, a feature length film typically consists ofanywhere from five to eight reels of film. However, those skilled in theart will recognize that the invention described herein for circumventingpiracy of motion pictures is not limited in its application to filmmedia, but can instead be used with any media on which a motion picturecan be stored. Such media can include any of a wide variety of existingtechnologies including DVD, CD ROM, and magnetic disc as well as anyother solid state, optical, electro-optical, magneto-optical storageformats as are now known or which may become known in the future.

FIG. 1 is a representation of a motion picture stored on a medium 100. Aprocess for uniquely identifying each production copy of the motionpicture that is printed for distribution to theaters can begin byselecting two or more scenes of the motion picture. Each of the scenescan comprise an identifiable portion of the motion picture distinct fromevery other portion of the motion picture. In FIG. 1, scenes 102 ₁through 102 _(n) are shown, it being understood that the invention isnot limited to any particular number of selected scenes.

Once the scenes 102 ₁ through 102 _(n) have been chosen, two or moresequences 104 can be defined within each of the scenes. The sequences104 are preferably of equal length and each sequence can include one ormore frames 106 that contain image information. For example, within amotion picture, three scenes 102 ₁, 102 ₂, 102 ₃, can be identified andeach scene can be divided into twenty eight sequences 104 ₀ through 104₂₇, with each of the sequences containing twelve frames 106 ₁ though 106₁₂. Notably, the number of scenes and the number of associated sequencescan be selected to provide a desired number of possible identifiercombinations. For example, the number of possible identifiercombinations can be equal to the number of sequences 104 ₀ through 104_(n) in each scene 102 ₁, 102 ₂, 102 ₃ raised to a power equal to thenumber of scenes comprising an identifiable portion of the motionpicture. For example, if there are three scenes, each with 28 sequences,the number of possible identifier combinations can be 28³, or 21,952.

After the scenes 102 ₁, 102 ₂, 102 ₃ and associated sequences 104 ₀through 104 ₂₇ have been defined, two or more selected sequences fromeach scene 102 ₁, 102 ₂, 102 ₃ can be marked with an identifier mark toproduce a uniquely identifiable pattern. For example, referring to FIG.1, a particular motion picture print stored on media 100 can be markedso that in scene 102 ₁, sequence 104 ₉ is marked; in scene 102 ₂,sequence 104 ₁₄ is marked, and in scene 102 ₃, sequence 104 ₇ is marked.The film print can thus be assigned a serial number 9-14-7,corresponding to the number of the sequences marked with identifiermarks in each scene. In this way, the particular sequence or sequencesmarked within each scene define the code that allow a particularproduction copy of the motion picture to be identified.

Further, an additional scene can be identified for errordetection/correction by use of an exemplary check sum, for exampledepicted as scene 102 _(n) in FIG. 1. The error detection/correctionscene 102 _(n) also can be divided into a number of sequences 104 ₀through 104 _(n) equal in length to other selected scenes, for exampletwenty eight sequences 104 ₀ through 104 ₂₇. Again, each sequence cancontain one or more frames. For instance, each of the sequences canagain contain twelve frames 106 ₁ though 106 ₁₂. One or more of thesequences can be marked with an error detection/correction mark. Thismark can correlate to the sequence markings (identifier marking pattern)which allow a particular motion picture print to be identified. Inparticular, an error correction mark can enable the identifier markingpattern to be determinable in the absence of at least one of theidentifier marks. For example, if the identifier mark in a particularscene is unreadable, the error correction mark can be used to determinethe value represented by that identifier mark.

In one arrangement, for example where three scenes are selected tocontain identifier marks, a desired print identifier “P” can berepresented by the uniquely identifiable marking pattern as P═I₁+I₂M+ .. . +I_(n)M^(n-1), where: I₁ = P  Mod  M I₂ = Floor((P/M)Mod  M) ⋮I_(n) = Floor((P/M^(n − 1))Mod  M).The error correction number “E” can be expressed as:E=(I ₁ +I ₂ + . . . +I _(n))Mod M.

Using these equations, M is a constant. For example, M can represent thenumber of defined sequences 104 in each scene 102 ₁, 102 ₂, 102 ₃, 102_(n). Mod returns the remainder of the quotient derived by dividing theoperand immediately preceding “Mod” by the operand immediately following“Mod.” Floor rounds the remainder down to the nearest integer. I₁through I_(n) each can be an integer that correlates to an identifiermark, for instance an identifier mark associated with a particularsequence 104 ₀ through 104 _(n).

If any of the marks correlating to integers I₁ through I_(n) are missingor unreadable, the associated integer can be computed by subtracting theintegers correlating to the readable marks from the error correctionnumber “E.” This difference then can be divided by the constant “M,” andthe quotient can be rounded down to the next nearest integer. Forexample, if there are three integers I₁, I₂ and I₃ correlating toidentifier marks, and the mark to which I₂ correlates is unreadable, thefollowing equation can be used to determine I₂:I ₂=(E−I ₁ −I ₃)Mod M.

Equivalently, the associated integer can be computed by subtracting theintegers correlating to the readable marks from a sum of the constant“M” multiplied by an integer equal to the number of integers beingsubtracted in the formula and the error correction number “E”. Again,this difference then can be divided by the constant “M,” and thequotient can be rounded down to the next nearest integer. For example,if there are three integers I₁, I₂ and I₃ correlating to identifiermarks, and the mark to which I₂ correlates is unreadable, the followingequation can be used to determine I₂:I ₂=(2M+E−I ₁ −I ₃)Mod M.In this example M is multiplied by two because there are two integers(I₁ and I₃) that are being subtracted. This form of the equation caneliminate potential problems which may arise due to negative moduloarithmetic.

The following are specific examples of error correction implementation.

EXAMPLE #1

Assume there are three scenes selected for the identifier markingpattern, each having 28 sequences. Assume a print identifier of 659 isused. Thus,P=659M=28I ₁ =P Mod M=15I ₂=Floor((P/M)Mod M)=23I ₃=Floor((P/M ²)Mod M)=0E=(I ₁ +I ₂ +I ₃)Mod M=10.

An identifier mark can be applied to a sequence 104 ₁₅ in a first scene,a sequence 104 ₂₃ in a second scene, and a sequence 104 ₀ in a thirdscene. An error correction mark can be applied to a sequence 104 ₁₀ in afourth scene. If the identifier mark placed in third scene is notreadable, I₃ can be computed asI ₃=(2M+E−I ₁ −I ₂)Mod M=(2*28+10−15−23)Mod 28=0.

EXAMPLE #2

Assume there are four scenes selected for the identifier markingpattern, each having 36 sequences. Assume a print identifier of 79,636is used. Thus,P=79,636M=36I ₁ =P Mod M=4I ₂=Floor((P/M)Mod M)=16I ₃=Floor((P/M ²)Mod M)=25I ₄=Floor((P/M ³)Mod M)=1E=(I ₁ +I ₂ +I ₃ +I ₄)Mod M=10.An identifier mark can be applied to a sequence 104 ₄ in a first scene,a sequence 104 ₁₆ in a second scene, a sequence 104 ₂₅ in a third scene,and a sequence 104 ₁ in a fourth scene. An error correction mark can beapplied to a sequence 104 ₁₈ in a fifth scene. If the identifier markplaced in second scene is not readable, I₂ can be computed asI₂=(2M3M+E−I₁−I₃−I₄) Mod M=(23*36+10−4−25−1)Mod 36=16.

Nonetheless, the invention is not limited to the specific arrangementscontained herein. Any number of scenes can be selected to containidentifier marking pattern and any number of sequences can be selected.

The marking process can include the step of marking one or more frames106 that are contained within a particular sequence 104 _(n). In onearrangement, a same marking pattern can be used for each of theidentifier marks and the error correction mark. In another arrangement,a different mark can be used for each scene, depending on which integerthe scene represents in the identifier marking pattern. Further, adifferent mark can be used for the error correction mark.

According to a preferred embodiment, between two to five consecutiveframes can be marked anywhere within the sequence. For example, thefirst three frames appearing in a sequence can be marked. The markingcan be accomplished by modifying the medium to cause a mark to beassociated with a particular frame. Consequently, when the imageassociated with such frame is displayed, the mark will be visible. Themark which is formed can include a constellation of dots. Each of thedots can have a profile corresponding to a predetermined shape which canbe any suitable polygon, circular, elliptical shape. The color of themarking can be selected to enhance a contrast with an image associatedwith a frame so that the marking can be more easily detected at asubsequent time. Further, the constellation of dots can be varied byproduction location. Consequently, a uniquely identifiable constellationof dots can be associated with individual ones of a number of productionlocations. In this way, the constellation can also identify a particularproduction or printer location as well as the source or origin of thecopy theft.

According to one embodiment of the invention, the motion picture scenes102 ₁ through 102 _(n) can be selected so that they are separated fromeach other by a buffer section 103 of the motion picture comprising oneor more frames. Further, the motion picture scenes can be selected byidentifying portions of the motion picture that tend to lessen thepotential that a mark will be noticed by a viewer. Scenes having asubstantial amount of action therein can be advantageous as the viewer'seye is drawn to the motion in the scene and is therefore less likely tonotice the mark. However, scenes that include panning motion are lessdesirable because the mark will appear stationary as the background inthe scene moves with the camera pan. This is a disadvantage as it tendsto draw attention to the mark. The motion picture scenes can also beadvantageously selected by identifying portions of the motion picturethat have density, lighting and/or coloration characteristics thatenhance the visibility of the marking pattern.

According to another aspect of the invention, each of the sequenceswithin each scene can correspond to a number. In that case, the markingstep can include marking respective ones of the sequences in each of thescenes so that the combination of the numbers assigned to the sequencesthat are marked correspond to a film print identification numberassigned to the particular copy. The method can also include varying themarking pattern for each copy of the motion picture that is produced sothat no two copies of the motion picture have the same marking pattern.

The mark that is applied to a frame can include any modification of themedia that will produce a visually identifiable feature when the frameis displayed. For example, the feature can be a single dot, aconstellation or grouping of dots arranged in a particular pattern, apattern of straight or curved lines and any combination thereof. Dotscan be of any particular shape including circles, ovals, ellipses,polygons, and any other regular or irregular shape. Even a mark thatappears to be a random scratch can be used for this purpose, providedthat the scratch is readily identifiable when the frame is displayed.According to one embodiment, the choice of mark can be withoutlimitation, except to the extent that it can be identified at a latertime. This can be a significant advantage because the marks can beformed in such a way as to be relatively difficult to identify andremove by illicit copiers. Alternatively, the mark itself can be codedin such a way as to have some further meaning.

For example, where there exists more than one laboratory or productionfacility where prints are made, the mark can be used to identify theparticular printer location. In that case, different productionlocations can be assigned different marks. This concept is illustratedin FIGS. 2A and 2B. FIG. 2A shows a frame 106 that includes a mark 108that is comprised of a constellation of dots. The arrangement of thedots forming the constellation in FIG. 2A can signify a first productionlocation. In contrast, FIG. 2B shows a frame 106 with a second mark 108comprised of a constellation of dots having a different arrangement thatcan be used to identify a second production location.

Referring to FIG. 3, the mark 108 can be advantageously selected so thatit is not readily apparent to a viewing audience. Accordingly, it can bedesirable in that case to choose a mark 108 such that its individualelements, such as dots 110 or lines, are relatively small in size. Ofcourse, the mark must be of sufficient size so as to be observable whenthe frame image 112 is subsequently reviewed in an illicit copy.Further, the color of the mark or dots can be selected so that itprovides only enough contrast with the motion picture image of the frame106 ₁ on which the mark has been placed so as to be clearly identifiablewhen the image 112 contained in the frame 106 ₁ is displayed. The colorof the mark can also be varied for different scenes for this purpose.However, the invention is not limited in this regard and a single colorcould be used for all marks appearing in the various sequences andscenes.

A single frame could be used to mark a particular sequence for thepurpose of encoding the particular production copy of a motion picture.However, this can be a disadvantage because modern video compressiontechniques employed with certain types of copying devices can partiallyor completely remove such markings when they appear only in a singleframe. Referring again to FIG. 1, it can be advantageous for thepurposes of the present invention to mark a plurality of consecutiveframes 106 within a particular sequence 104, using the same mark havingthe same relative position within each frame. This consecutive markingwill help ensure that the marks survive any video compression algorithmapplied during the creation and/or distribution of legitimate or illicitcopies.

Increasing the number of consecutive marked frames can have drawbacks.In particular, increasing the number of consecutive frames that aremarked tends to increase the likelihood that a viewing audience willbecome aware of their presence. This can detract from the enjoyment ofthe motion picture or create the impression that a particular theaterdoes not show high quality films. Furthermore it can alert those whoillicitly record the motion pictures to the presence of the marks. Inthis regard, it has been found that two to five and preferably threeconsecutively marked frames strikes a satisfactory balance betweenaudience distraction whilst maintaining sufficient robustness of themarks. However, it will be appreciated that more or fewer marked framescan be used and the invention is not limited to any particular number ofconsecutively marked frames.

The same or different marks can be used in different scenes 102.However, marks used within a particular sequence 104 on a plurality ofconsecutive frames are advantageously made substantially similar to oneanother to avoid being lost when video compression techniques areapplied during subsequent illicit copying or transmission of the motionpicture.

Frames can be marked using any suitable method appropriate for the mediaon which the motion picture is recorded. For example, if a particularproduction copy of the motion picture is recorded on a film media, thenthe image on a frame of the film can be modified in a manner similar tothat which is used with conventional CAP coding. Such techniques arewell known in the art. Still, those skilled in the art will appreciatethat there are a wide variety of well known methods for placing anidentifiable mark on one or more motion picture film frames that will bevisible when the frame is displayed and the invention is not limited toany particular method. For example, the mark can be added to the filmmedia at the time the film is printed. The marking can be accomplishedusing lasers to embed the mark, a film strip projector or slideprojectors to overlay the mark on the film stock, a digital lightprojector (DLP) or any other suitable means to create on a particularframe of a film print an image corresponding to the desired mark.

Other, less sophisticated, means also can be used to mark the filmstock. For example, a scratch tool could be used to manually scratch themark into the film at the appropriate locations. However, this type ofmanual marking can lead to inconsistencies in the mark and therefore isnot the preferred manner of marking. Marks can also be applied to thefilm directly with ink.

If the motion picture is digitally recorded, then the digital dataassociated with such recording medium can be modified in such a way asto produce the selected mark. For example, conventional DVD media can bemodified so that a selected image will be caused to be overlaid on theimage associated with one or more frames. If the selected image is thedesired mark, then those particular frames within a marked sequence willappear to have the mark superimposed thereon when displayed. This imagewould be reproduced if the motion picture was recorded using a camcorderor other type of video recording device. Of course, those skilled in theart will appreciate that the particular type of recording media andcompression scheme will affect the manner in which the digital data ismodified and such methods are within the ordinary skill in the art. Inthis regard, the invention is not limited to any particular digitalrecording medium, video compression scheme, or method of modifying thedigital media to associate the mark with the selected scenes of themotion picture. Any suitable method can be used to modify the digitaldata of the media in order to add the mark to a frame of the motionpicture. Further, it should be noted that the word frame as used hereincan include interlaced as well as non-interlaced video frames.

Notably, the coding process described herein can be repeated multipletimes at various different locations on the media 100 on which themotion picture is disposed. In that case a second group of scenes 102can be selected, each comprising an identifiable portion of the motionpicture distinct from every other portion of the motion picture. As withthe first group of scenes, two or more sequences 104 can be definedwithin each of the second group of motion picture scenes, with each ofthe sequences including two or more frames 106. Thereafter, the methodcan continue as described above, by marking at least one of thesequences from each of the second group of scenes to repeat the uniquelyidentifiable marking pattern. Alternatively, if the second group ofscenes is contained on a second reel of film, a different coding patterncan be used.

The invention can also include an apparatus for producing a motionpicture disposed on a film media that includes the anti-piracy coding.Referring to FIG. 4, the apparatus 400 can create a coded productioncopy of a motion picture from a motion picture film negative 407. Theapparatus can include a control computer 414 communicating with anencoder 416 and a marking device 412. A production copy of a motionpicture can be created from a reel 402 of unexposed film stock 401 bypassing the film through a printer 418. Printer 418 can be any of avariety of commercially available film print machines that is capable ofcreating a motion picture film print from film negative 407. Filmnegative 407 can be passed from reel 406 containing film negative to beprinted, to reel 408 that spools film negative that has already beenprinted. Similarly, film stock 401 can be transferred from reel 402containing unexposed film stock to reel 404 containing film that hasbeen printed. Film stock 401 is passed through the printer 418concurrently with film negative 407 and each frame of the film negativeis transferred to the unexposed film stock 401 in the conventionalmanner well known to those skilled in the art.

As the motion picture images are transferred frame by frame from filmnegative 407 to film stock 401, the number of frames 106 that have beenprinted can be counted using information provided by encoder 416.Encoder 416 can be any of a variety of commercially available devicescapable of counting frames 106 as the film is spooled from reel 402 toreel 404. For example, the encoder can be a sprocket wheel that engagessprocket holes in the print film 401. A shaft (not shown) can beoptically encoded so that its rotation can be counted using anelectro-optical sensor. Alternatively, any other type sensor includingan electrical, electro-optical, mechanical or electro-mechanical sensorcan be used for this purpose, provided that it is capable ofcommunicating information to control computer 414 that directly orindirectly relates to the number of frames of film that are passed overthe sprocket.

The code number corresponding to each production copy of a motionpicture can be added to the media on which the production copy isdisposed. For example, according to one embodiment, a scannable bar codecan be burned onto the film stock using a laser 410. This can allow forconvenient identification of the particular production copy withoutsearching for the anti-piracy coding marking as described herein. Thebarcode can be located in the leader area of the printed reel of film.Alternatively, the barcode can be placed onto the areas outside of orbetween the perforations in the film. Such placement can be advantageousfor preventing the barcode from becoming visible to an audience viewingan exhibition of the motion picture. The laser 410 can be controlled bycontrol computer 414 to produce the proper bar code on each filmcorresponding to the anti-piracy markings that have or will be added.

The present invention can be realized in hardware, software, or acombination of hardware and software. Control computer 414 can berealized in a centralized fashion in one computer system, or in adistributed fashion where different elements are spread across severalinterconnected computer systems. Any kind of computer system or otherapparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware and software can be a generalpurpose computer system with a computer program that, when being loadedand executed, controls the computer system such that it carries out themethods described herein.

The present invention also can be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemarranged as shown in FIG. 4 is able to carry out these methods. Computerprogram in the present context means any expression, in any language,code or notation, of a set of instructions intended to cause a systemhaving an information processing capability to perform a particularfunction either directly or after either or both of the following: a)conversion to another language, code or notation; b) reproduction in adifferent material form.

Control computer 414 can be provided with information regarding specificportions of the production copy of the motion picture that are to bemarked. This information can be provided in any one or more of severaldifferent ways. According to one embodiment, the control computer can beprovided with specific frame numbers relative to a reference point (e.g.the beginning of the motion picture) that are to be marked.Alternatively, the control computer can be provided with specificphysical locations that are to be marked relative to the beginning ofthe film print. These specific physical locations can correspond to aset of frames within the sequence that is to be marked. In anotherembodiment, the control computer 414 can be provided with informationidentifying the scenes (e.g. by a range of frame numbers) within thefilm that are to be marked, the number of sequences within each scene,and the particular code number assigned to the particular productioncopy of the motion picture. The control computer 414 can then use thisinformation to automatically identify the frame numbers that areassociated with each sequence 104, and the specific sequence of framesthat need to be marked in order to code the particular production copyof the film with the code number that has been assigned to it.

The control computer can also be programmed with information relating tothe number of consecutive frames to be marked within each of thesequences, and the location of the frames (e.g. first three frames) thatare to be marked within each marked sequence. Control computer 414 cancontrol the selection of frames that are marked based on informationprovided by encoder 416 and control information from printer 418regarding the number of frames that have been printed relative to somereference point such as the beginning of the film.

In FIG. 4, the marking process is shown occurring immediately after theprinting process. However, those skilled in the art will appreciate thatthe invention is not limited in this regard. For example, the markingcould be performed anytime before or after the motion picture istransferred to the film stock 401. The invention is also not limited tothe precise arrangement shown in FIG. 4. For example, the marking devicecould conceivably be arranged to mark the film stock 401 before the filmis fed to the printer 418.

An exemplary serial number recovery sequence is shown in FIG. 5, where aprint copy, serialized in accordance with the inventive arrangements, isanalyzed to determine and reconstruct the serial number of the originalfilm print. The print copy may be stored on various media such as film,magnetic tape or disc, optical disk, solid state memory or the like andmay consequently be impaired requiring error detection and correction inaddition to serial number recovery. Error detection and correction isperformed in the event that part or parts of the print identifying marksare absent or rendered indeterminate.

Serial number determination starts at block 500 with the storage mediumbeing played or read out at block 510. The storage medium may be played,searched or addressed to find a start scene location, depicted as block520 in FIG. 5, and scene 102 ₁ in FIG. 1. Although the location of eachscene within the film print is known to the original print maker, thespecific frame count or footage location may not be faithfullyreplicated in a copy whether illicit or legitimate. Hence thedetermination of successive start scenes, for example 102 ₁, 102 ₂, 102_(n) etc. may necessitate operator scrutiny.

Locating the occurrence of marked frames 106 ₁, 106 ₂, 106 ₃ present inrespective sequences 104 ₁, 104 ₂, 104 _(n) of FIG. 1 is performed atdecision block 530 of FIG. 5, and may be performed automatically but mayalso necessitate further operator scrutiny since the sequence locationmarks within each scene are specific to each individual serial number.If decision block 530 is satisfied (YES) the process continues at block540. However, if the sequence mark is not located, block 530 indicatesNO and forms a loop via decision block 535 to block 520 to eitherrelocate and re-search the initial scene termed a recursive search or tolocate and search another scene termed a non-recursive search. Forexample, this loop can represent an automated or operator search or acombination where for example, an automated system performs a initialcheck to establish the presence of a sequence mark and in the event offailure to detect the mark signals for human mark recognition as a finalstep before abandoning a particular scene and proceeding to the nextmarked location.

The number of loops traversed to determine sequence marks is counted andtested for equality to a predetermined value M at decision block 535.For example if two attempts are permitted M=2, thus when block 535 testsYES the two attempts have failed and block 545 causes the next scenestart to be located at block 520. Once again decision block 530identifies the location of the next marked frame sequence as has beendescribed.

Automated marking pattern recognition can be performed when the originalprint copy is marked as described previously, for example with aprescribed constellation of dots, of specific shapes and or colors.Having located one or more of the marked frames (106) the actualsequence number can be determined, at block 540, relative to thebeginning of the specific scene with this sequence number stored atblock 550. For example, in FIG. 1, scene 102 ₁ is depicted with markedframes (106 ₁, 106 ₂, 106 ₃) occurring in the ninth sequence (104 ₉),thus sequence number 9 is stored at block 550.

At block 560 a test is performed to determine if all the requiredsequence numbers forming the serial number and check sum have beenrecovered and stored. For example in FIG. 1, the number of serial numbercomponents N represents 4 where three components identify the serialnumber with the fourth representing the error detection/correction codenumber. If block 560 tests NO a loop is formed via block 570 whichrepeats blocks 520 through 570 to locate the sequence numbers untilblock 560 tests YES.

Having determined and stored all the required serial number components,the serial number of the print from which the subject copy (510) wasmade can be determined (at block 590) by suitable calculation not shownbut described previously, with the serial number determination processending at block 600.

An error correction code, for example a check sum, is included with thesequence numbers to allow recovery of the serial number despite adefective or poorly resolved sequence mark. At block 595 a forward errorcorrection calculation can be performed using stored sequence numberdata from a memory associated with storage block 550. Error correctioncalculation, as previously described can be invoked by the absence ofany one of the serial number determining components. However, for errorcorrection to be performed some number of the serial number determiningcomponents plus the error correction code must have been recovered andstored.

Returning to block 560 testing NO. Since the exemplary number of serialnumber components (N) is 4 the repeat loop formed via block 570 musttraverse blocks 520 through 570 no more than 3 times or more generally(N−1). Thus at decision block 570 a test is performed to determine ifthe number of repeat loops has exceeded N which is indicative of afailure to determine and store one or more of the serial number and orerror correction code components. If decision block 570 tests YES theserial number is indeterminate and the process is terminated at endblock 600.

As has been described, an error detection and correction code isadvantageously included as part of each serialized motion picture printcopy with FIG. 1 depicting the FEC code within a final scene. However,the scene start or temporal location of this error correction code is inno way limited to the location depicted. The advantageous FEC code canbe arbitrarily located at any scene start location within the print copywith the location chosen based on criteria similar to that employed forthe serial number scene locations. Clearly to enable serial numberrecovery from subject copy it is necessary to know not only the numberof serial number components, their respective scene start locations butalso the serial number component order. For example whether the FEC codeis located after or ahead of the serial number components or possiblyinterleaved therewith. Furthermore a database which relates print serialnumber or bar code with exhibitor location will in addition provide therequired title specific meta data to enable serial number derivation.The exemplary sequence of FIG. 5 represents a sequence of events to berealized by operational use of hardware, software, or a combination ofhardware and software.

As described above, and in accordance with the inventive concept, aprint identifier is mapped to an erasure-correcting coded serial numberfor use in tracking the copy of the motion picture. The copy of themotion picture is then marked in accordance with the erasure-correctingcoded serial number. Illustratively, the erasure-correcting coded serialnumber is mapped to particular sequences of the copy of the motionpicture and at least one frame of each particular sequence is markedwith an identifier.

An illustrative block diagram of an encoder 750 in accordance with theprinciples of the invention is shown in FIG. 6. Encoder 750 comprises amapper 755 and a coder 760. Mapper 755 maps (or encodes) a printidentifier into the first set of J numbers. Coder 760 operates on atleast a portion of this first set of numbers to provide a number oferror correction numbers, K, where K>0. These error correction numbersare also referred to herein as redundant data. The second set of Lnumbers comprises the error correction numbers, K, along with the firstset of J numbers. As a result,L=J+K.The second set of L numbers represents the sequence of numbers used tomark the copy of the film.

It should be noted that it is not necessary for the marks to representexclusively error correction values or print identifier values. Inaccordance with the principles of the invention, error correction andidentifier values can be mixed. Indeed, other, more flexible codes mayalso be created. For example, it might be desirable to create a codethat would allow films with only a few serial numbers to be decoded suchthat if M marks are missing, where M>1, the print identifier can stillbe recovered. This could be desirable in the context of marking alimited production run, e.g., if only a limited number of copies wereproduced (e.g., 500). In this context, an illustrative code is describedbelow where error correction and identifier values are mixed.Alternatively, this illustrative code can also be used to recover aprint identifier even if two marks are missing.

Again, let P equal a print identifier number. This print identifier, P,is then encoded, or mapped, into a first set of J numbers.Illustratively, J=3, i.e., the print identifier, P, is encoded intothree numbers, A, B and C, as illustrated below.A=P mod M;B=Floor(P/M)mod M; andC=Floor(P/M ²)mod M.In addition, this first set of numbers is further mapped, or encoded,into a second set of L numbers (also referred to herein as anerasure-correcting coded serial number). Illustratively, L=4, i.e., thefirst set of numbers is encoded into four numbers, W, X, Y and Z, asillustrated below.W=A;X=B;Y=(A+B+C)mod M; andZ=(A+2B−2C)mod M.The second set of numbers represent the particular sequence numbers thatare marked in the film copy in the following order: W, X, Y and Z. Itcan be observed from the equations used to determine the second set ofnumbers that identifier values and error correction values are mixed. Inparticular, the identifier value C of the first set is mixed into thevalues of Y and Z of the second set. These latter values are used toprovide error correction. In other words the second set of L numbersonly includes N numbers of the first set of J numbers, N<J. Theremainder of the J numbers, R, are derived as a function of one, ormore, of the J numbers. In this example, Y and Z are derived as afunction of all three numbers: A, B and C.

In terms of recovering the print identifier from a marked copy of thefilm encoded as shown above, the illustrative flow chart of FIG. 7 isused in conjunction with table one of FIG. 8. In steps 705 and 710 ofFIG. 7, the scene start for each mark is determined and the location ofthe mark in each scene is determined, respectively. In step 715, thedifference is divided by the offset per sequence value. In step 720, anythree marks associated with the second set of numbers are found. Fromthese three marks, the missing sequence number is identified and thefirst set of numbers is recovered in step 725. Turning briefly to FIG.8, table one illustrates a set of equations for determining the missingsequence number. In particular, once the missing sequence number isidentified, that set of equations in the associated column of table oneis used to determine the first set of numbers. It should be noted thatany results from the equations shown in table one are further reducedMod M. Returning to FIG. 7, once the first set of numbers is determined,then the print identifier is recovered in step 730 in accordance withthe following equation:P=A+(3*B)+(961*C).

In the context of a further illustration, assume M=31, i.e., mod 31 isused. Further, assume that a print identifier, P, is equal to 15,152. Assuch, using the equations noted immediately above, the print identifier,P, is encoded into the following first set of numbers:A=24;B=23; andC=15.This first set of numbers is then further encoded into the followingsecond set of numbers:W=24;X=23;Y=0; andZ=9.As such, a copy of the film to be associated with the print identifier15,152 would be marked in accordance with the sequence numbers 24, 23, 0and 9.

When attempting to recover the second set of numbers from the copy ofthe film, assume that only the numbers X, Y and Z were found, i.e., W ismissing. From table one of FIG. 8, the set of equations in the columnassociated with W is used to recover the first set of numbers, as shownbelow:A=(2*0+9−4*23)*21=−1743=24 mod 31.B=23; andC=(23+0−9)*21=294=15 mod 31.Once the first set of numbers is determined, the print identifier, P, isrecovered:P=24+23*31+15*961=15,152.

If the number of film copies is less than 960, and further in accordancewith the principles of the invention, the above-identified code can beused to recover a print identifier even if two marks are missing. Again,assume M=31, i.e., mod 31 is used. Further, assume that a printidentifier, P, is equal to 123. As such, using the equations notedimmediately above, the print identifier, P, is encoded into thefollowing first set of numbers:A=30;B=3; andC=0.This first set of numbers is then further encoded into the followingsecond set of numbers:W=30;X=3;Y=2; andZ=5.As such, a copy of the film to be associated with the print identifier123 would be marked in accordance with the sequence numbers 30, 3, 2 and5.

When attempting to recover the second set of numbers from the copy ofthe film using, e.g., the flow chart of FIG. 7, assume that only thenumbers Y and Z were found, i.e., X and W are missing. In this example,the flow chart of FIG. 7 is used in conjunction with table two of FIG.9. From table two, the set of equations in the row associated with thefound pair of numbers (here, Y and Z) is used to recover the first setof numbers, as shown below:A=(2*2−5)=−1=30 mod 31; andB=5−2=3.Again, it should be noted that any results from the equations shown intable two are further reduced Mod M. Once the first set of numbers isdetermined, the print identifier, P, is recovered in accordance with thefollowing equation:P=A+(31*B)+(961*C).In this particular example,P=30+31*3=123.

An illustrative block diagram of an encoder 765 in accordance with theprinciples of the invention is shown in FIG. 10. Encoder 765 comprises amapper 755 and a coder 770. Mapper 755 maps (or encodes) a printidentifier into the first set of J numbers. Coder 770 operates on atleast a portion of this first set of numbers to provide a number oferror correction numbers, K. The second set of L numbers comprises theerror correction numbers, K, along with a portion, N, of the first setof numbers, J, where N<J. As a result,L=N+K.

In other words, R of the numbers (in the first set of J numbers), whereR>0, are not shown explicitly as a part of the identifier values but areencoded into the error correction numbers, K. In the context of theexamples shown in FIGS. 7, 8 and 9, and described above, J=3, K=2 andR=1 (i.e., the identifier value C was mixed into the values of Y and Z).The second set of numbers represents the sequence of numbers used tomark the copy of the film.

Another more general form of an encoder in accordance with theprinciples of the invention is shown in FIG. 11. Encoder 775 comprisesmapper 755 and coder 780. Mapper 755 maps (or encodes) a printidentifier into the first set of J numbers. Coder 780 operates on atleast a portion of this first set of numbers to provide the second setof L numbers, where L>J.

Although the error correcting codes illustrated and described herewithare erasure correction codes, it will be clear that the invention is notso limited. In particular, any error detection or correction code couldbe used, including, for example, Reed-Solomon codes, BCH codes, Hammingcodes, or any other desired correction code. In this regard, althoughthe inventive concept was illustrated in the context of recovering from“missing” numbers, the inventive concept also applies to recovering from“corrupted” numbers.

In view of the above, the foregoing merely illustrates the principles ofthe invention and it will thus be appreciated that those skilled in theart will be able to devise numerous alternative arrangements which,although not explicitly described herein, embody the principles of theinvention and are within its spirit and scope. It is therefore to beunderstood that numerous modifications may be made to the illustrativeembodiments and that other arrangements may be devised without departingfrom the spirit and scope of the present invention as defined by theappended claims. For example, although illustrated in the context ofscenes and sequences, equivalent methods of partitioning a film may beused such as, but not limited to, dividing a film into zones based onfilm footage, each zone having a predefined film footage and comprisinga number of sequences.

1. A method for identifying a copy of a motion picture comprising:generating a sequence of J numbers representing a serial number for thecopy of the motion picture; creating at least two error-correctingnumbers, X and Y, each a function of one or more of the J numbers; andmarking the copy of the motion picture with at least the twoerror-correcting numbers X and Y.
 2. The method of claim 1, wherein theat least two error-correcting make up an erasure-correcting coded serialnumber having L numbers that enables recovery of a print identifierassociated with the copy of the motion picture if M of the L numbers aresubsequently missing, or corrupted.
 3. The method of claim 1, whereinthe serial number is a print identifier for the copy of the motionpicture.
 4. The method of claim 1, wherein the generating step maps aprint identifier for the copy of the motion picture into the sequence ofJ numbers.
 5. The method of claim 1, wherein the at least twoerror-correcting numbers are represented by marks on various frames ofthe copy of the motion picture.
 6. A method for identifying a copy of amotion picture disposed on a medium comprising the step of: marking thecopy of the motion picture in accordance with an erasure-correctingcoded serial number; wherein the erasure-correcting coded serial numbercomprises L numbers and the erasure-correcting coded serial numberenables recovery of a print identifier associated with the copy of themotion picture if M of the L numbers are subsequently missing, whereM>1.
 7. The method of claim 6, wherein the erasure-correcting codedserial number is represented by identifier marks and at least one errorcorrection mark on various frames of the copy of the motion picture. 8.The method of claim 6, wherein the marking step includes the steps of:marking each of at least a first sequence and a second sequence of thecopy of the motion picture with the identifier marks; and, marking atleast a third sequence of the motion picture with the at least one errorcorrection mark, wherein absent M of the marks, the erasure-correctingcoded serial number is determinable by processing the remaining ones ofthe marks.
 9. The method of claim 6 wherein the erasure-correcting codedserial number represents a print identifier.
 10. A method foridentifying a copy of a motion picture disposed on a medium comprisingthe step of: providing a first set of J numbers, which are associatedwith a print identifier of the copy of the motion picture, coding atleast a portion of the first set of J numbers to provide a second set ofK numbers where K>1; and marking the copy of the film in accordance witha sequence of L numbers, where N of the L numbers are taken from thefirst set of J, and the remainder of the L numbers comprise the secondset of K numbers.
 11. The method of claim 10, wherein the L numbersrepresent an erasure-correcting coded serial number.
 12. The method ofclaim 10, wherein the marking step includes the steps of: markingrespective sequences of the copy of the motion picture in accordancewith the N numbers from the first set of J numbers; and markingrespective sequences of the copy of the motion picture in accordancewith the second set of K numbers.
 13. A method for use in identifying acopy of a motion picture disposed on a medium comprising the step of:displaying the copy of the motion picture with an erasure-correctingcoded serial number represented therein; wherein the erasure-correctingcoded serial number comprises L numbers, wherein N of the L numbersrepresent a portion of a serial number comprising J numbers, the serialnumber being associated with the copy of the motion picture, and theremainder of the L numbers represent the remaining J-N numbers of theserial number in encoded form, where L>J+1.
 14. The method of claim 13,wherein the erasure-correcting coded serial number is represented byidentifier marks and an error correction mark disposed on a plurality offrames of the copy of the motion picture.
 15. The method of claim 13wherein the erasure-correcting coded serial number represents a printidentifier.
 16. A readable medium for storing a motion picture, themotion picture comprising: a plurality of frames, each framerepresenting a portion of the motion picture, wherein some of the framesare marked to represent an erasure-correcting coded serial number;wherein the erasure-correcting coded serial number comprises L numbers,wherein N of the L numbers represent a portion of a serial numbercomprising J numbers, the serial number being associated with the copyof the motion picture, and the remainder of the L numbers represent theremaining J-N numbers of the serial number in encoded form, where L>J+1.17. A readable medium for storing a motion picture, the motion picturecomprising: a plurality of frames, each frame representing a portion ofthe motion picture, wherein some of the frames are marked to representan erasure-correcting coded serial number; wherein theerasure-correcting coded serial number comprises L numbers, and whereinthe erasure-correcting coded serial number enables recovery of a printidentifier associated with the copy of the motion picture if M of the Lnumbers are subsequently missing, where M>1.
 18. A readable medium forstoring a motion picture, the motion picture comprising: a plurality offrames, each frame representing a portion of the motion picture, whereinsome of the frames are marked to represent an erasure-correcting codedserial number; wherein the erasure-correcting coded serial numbercomprises L numbers, and wherein the erasure-correcting coded serialnumber enables recovery of a print identifier associated with the copyof the motion picture if M of the L numbers are subsequently corrupted.19. Apparatus for uniquely identifying a copy of a motion picturedisposed on a medium, the apparatus comprising: means for generating asequence of J numbers representing a serial number for the copy of themotion picture; and means for marking the copy of the motion picture inaccordance with an erasure-correcting coded serial number comprising Lnumbers, where L>J, and N of the J numbers are directly included in theerasure-correcting coded serial number, where L>J+1.
 20. The apparatusof claim 19, wherein the erasure-correcting coded serial number enablesrecovery of a print identifier associated with the copy of the motionpicture if M of the L numbers are subsequently missing, where M>1. 21.The apparatus of claim 19, wherein the erasure-correcting coded serialnumber enables recovery of a print identifier associated with the copyof the motion picture if M of the L numbers are subsequently corrupted.22. The apparatus of claim 19 wherein the serial number is a printidentifier for the copy of the motion picture.
 23. The apparatus ofclaim 19, wherein the means for generating maps a print identifier forthe copy of the motion picture into the sequence of J numbers.
 24. Theapparatus of claim 19, wherein the erasure-correcting coded serialnumber is represented by identifier marks and an error correction markon various frames of the copy of the motion picture.
 25. Apparatus foruse in marking a copy of a film with a serial number comprising Jnumbers, the apparatus comprising: a coder for encoding at least aportion of the J numbers into an erasure correcting coded serial numbercomprising L numbers, wherein N of the L numbers represent a portion ofa serial number, and the remainder of the L numbers represent theremaining J-N numbers of the serial number in encoded form, where L>J+1.26. The apparatus of claim 25, further comprising a mapper, whichgenerates the serial number from a print identifier to be associatedwith the copy of the film.